If you’re considering a water tank for your property, there are a few things you’ll need to do first.

We’ve written up this short guide so that you can calculate for yourself what size tank you’ll need and how much water you can expect to collect each year.

The first step is to find out exactly what your water requirements are — and what you can realistically harvest. To start with, calculate your current household water usage. If you have your water bill handy, this should be simple to find out. Otherwise, you can use a calculator such as this one, to make an estimate.

For this guide, we’ll work using some averages. In rural Victoria, the average annual rainfall for many people is around 750mm and average household water usage is 113 litres per day, per person. However, you will need to look up the average annual rainfall on the BOM website, to get a more accurate result for your area. For an average 4-person household, this works out to an average of 452 litres per day. Please note that this only includes a small amount of water for a very small courtyard style garden. Individual household water use will vary considerably depending on lifestyle and the behaviour of the respective members in the household.

Next, we’ll need to determine your catchment area. This is simply the available space to capture water for the tank. For most residential properties, this will be your roof area. For reference, an average 3 bedroom home has a roof area of 200m2. The following tool can help you calculate your catchment area.

Keep in mind, that for larger rural properties, the catchment area can be expanded by using our water collecting gutter system. This will enable you to capture more water than would usually be possible.

How big should my water tank be?

With these two figures, combined with your catchment area and water usage, we can now calculate the optimum size for a water tank to suit your needs.

Taking a 4-person household, for example, located in rural Victoria, with 452 litres usage a day, and an average roof area of 200m2, we can head over to the Alternative Technology Association’s Tankulator tool. This will help us calculate the right size tank and an idea of how much water we can save.

Our example situation recommends a tank size of 135,000 litres, which will save 165,710 litres of water a year.

What will it cost?

Of course, this is a broad question, but once you know what size water tank you need, this will be easier.

Looking at our pricing table, we can see that our recommended 135,000 litre tank will cost between $10,350 and $11,300.The benefits of having your own supply of clean drinking water is an advantage in itself, even before factoring in the added benefits of fewer water restrictions, particularly if you have your own bore for your gardening needs. In a rural situation, where it is not possible to access scheme water, you need to make the best decision for your family about what quality of tank you will invest in.

Heritage Water Tanks pride themselves in manufacturing and installing the best quality water tanks in Australia. Our liner is an Industrial grade liner and our BlueScope Steel tank walls are a solid 1mm thick.

How much will I save?

The average Victorian water usage charge is $2.7186/kL, pls $1.88/kL for sewerage disposal. Based on your 165,710 litre annual water saving from the water you would collect from a 135,000L rainwater tank, you would achieve an offset cost saving of $758/year. This might seem like a small saving to your annual budget, relative to a large capital investment of approximately ten to eleven thousand dollars, however, in areas with no access to scheme water, the cost of connecting the property to your local utility scheme water supply could potentially run into the hundreds of thousands of dollars.

If you’re interested in getting a quote on a steel water tank, or have other questions, just fill out our contact form or give us a call.